Agricultural metering systems are used to meter and dispense a wide variety of agricultural materials including seed, fertilizer, insecticide and herbicide, to a growing medium such as soil. Although generally in dry particulate form, some agricultural materials such as fertilizer, herbicide and insecticide are also in liquid form. Regardless of the particular form in which the agricultural material has, it is critical that the material be accurately and consistently dispensed and metered to the growing medium to insure maximum crop yield at the lowest cost.
A wide variety of agricultural material metering systems are generally available depending upon the type and form of material being metered and the desired metering accuracy and consistency. Such metering systems typically include a rotatable metering member which meters the agricultural material upon being rotated. To meter dry particulate material such as seed, fertilizer, insecticide or herbicide, such rotatable metering members typically include a detent such as a depression, hole or groove, which segregates and carries a distinct amount of material through a tube or other passage for delivery to the growing medium.
For example, Cyclo metering systems are typically used to meter and dispense seed. Cyclo metering systems typically includes a rotatable drum which receives seed from a hopper, wagon or cart and which meters the material into a furrow created by a ground engaging tool. The drum includes a plurality of openings which receive and carry the seed to seed delivery tubes as the drum is rotated. To insure consistent results, the interior of the drum is pressurized by a fan or blower to hold individual seeds against the openings as the drum is rotated. When the openings are closed off above the seed tubes, the seeds fall from the openings into the corresponding seed tubes for delivery to the growing medium.
A second type of agricultural material metering system is the plate seeder. Conventional plate seeders include a rotatable plate having a plurality of openings therethrough about its outer perimeter. With such plate systems, seeds are delivered to a first side of the plate while a fan or blower creates a vacuum on a second opposite side of the plate. This vacuum draws and retains individual seeds in the openings against the plate. During rotation, the plate carries the seeds to locations above seed delivery tubes where the vacuum is broken such that the seeds fall out of the holes into the tubes for delivery to the growing medium.
A third type of agricultural material metering system are cylindrical wheels or flutes. Such wheels or flutes are commonly used on carts on air seeding implements. The flutes are typically located at the bottom of a material compartment and are fed material by gravity. The material generally flows past an adjustable sliding panel or gate and is metered by the flute into an air tube for delivery directly to a growing medium or for delivery to a secondary metering system. The flutes typically include a plurality of axially extending teeth or grooves sized to carry and meter the agricultural material at a generally precise rate dependent upon the rate at which the flute is rotated.
Whether a drum, a plate or a flute, such rotatable metering members must each be rotatably driven to meter agricultural material. As a result, many of these systems employ mechanical ground drives which are mounted on the implement main frame. The ground drives typically include a ground engaging wheel and a mechanical drive train consisting of one or more chains and sprockets extending between the ground engaging wheel and a lengthy drive shaft connected to each of the rotatable metering members. Although commonly used, such mechanical ground drives have several associated drawbacks. Because the mechanical drive train is directly connected to the rotatable metering member, adjusting the location of the rotatable metering member to accommodate different row spacings is difficult if not impossible. Moreover, with such mechanical drive trains used to rotate rotatable metering members, different metering rates require multiple sprockets which occupy valuable space, which are subject to breakage and wear and which increase the cost of the system. In addition, adjusting the rate at which material is metered requires one or more chains to be repositioned and connected to different sprockets. Such a procedure is inconvenient and time consuming. Because the implement must generally be stopped to enable one or more chains to be repositioned, such systems do not allow the operator to adjust the rate at which material is metered while crossing the field or on the go.
In lieu of using a mechanical ground drive to drive the shaft connected to each rotatable metering member, some systems have alternatively used a mechanical ground drive to drive a hydraulic pump to drive hydraulic motors connected to rotatable metering members. Although eliminating the lengthy drive shaft extending between multiple metering members, such systems additionally require an independent hydraulic system with an additional hydraulic reservoir. Sometimes, a hydraulic cooler must be added also, but the rate of the meters still changes as the temperature of the oil in the system increases. With most hydraulic components used on agricultural implements, their volumetric efficiency decreases with increase in oil temperature and hence application rates uncontrollably. This increases both the cost and complexity of the system. Moreover, to adjust the metering rate, such systems still require that the chain of the mechanical drive train be repositioned on a multi-sprocket transmission. As a result, these systems are extremely space consuming and expensive and cannot be adjusted on the go while crossing a field.
In recent years, agricultural material metering systems have been developed which allow the material metering rate to be adjusted on the go while crossing a field. Such systems typically omit mechanical ground drive assemblies and instead rely on electronics to control hydraulic systems for accurate metering. In particular, such systems typically include ground speed sensors, such as radar, to detect ground speed of the work vehicle pulling the implement carrying the metering system. This sensed ground speed is transmitted to the system's electronics which control a series of hydraulic pumps and valves to hydraulically drive a hydraulic motor connected to each rotatable metering member. To adjust the metering rate of the electronic system, the user simply enters in a new desired rate. Based upon the newly entered rate, the electronics controls the hydraulic system to adjust the hydraulic oil flow sent to the hydraulic motor to adjust the rate at which the rotatable metering member is rotated.
Although such systems enable the metering rate to be adjusted on the go, such electronic metering systems are extremely expensive to implement and are difficult to diagnose and repair when damaged. Moreover, as compared to ground driven mechanical metering systems, such electronic metering systems require an additional hydraulic circuit to drive the hydraulic motors connected to the rotatable metering members. This additional hydraulic circuit increases hydraulic requirements of the work vehicle or tractor and when connected to open center hydraulic systems, can cause overheating problems.
Thus, there is a continuing need for an agricultural material metering system that is inexpensive, that is adjustable on the move, that enables the metering member to be easily repositioned and that does not increase the hydraulic requirements of the work vehicle or tractor.